15ml glass dropper bottle
1/32 tsp of powder = 135mg
~15ml distilled water (fully dissolved)
= 20mg PB2 = 0.13% solution
/
1/16 tsp of powder = 270mg
~15ml distilled water (not fully dissolved)
~15ml vodka (fully dissolved)
40mg PB2 = 0.26%
The study I saw on procyanidin B2 for hair used a 1% strength procyanidin B2 solution. But this apple skin powder has additional polyphenols and procyanidins in it other than just B2, so it might be comparably "strong."
https://img.cosmeticsandtoiletries.com/files/base/allured/all/image/2020/06/ct.CT_116_12_061_09.pdf